“If the past is a foreign country, it is a shockingly violent one. It is easy to forget how dangerous life used to be, how deeply brutality was once woven into the fabric of daily existence. Cultural memory pacifies the past, leaving us with pale souvenirs whose bloody origins have been bleached away. A woman donning a cross seldom reflects that this instrument of torture was a common punishment in the ancient world; nor does a person who speaks of a whipping boy ponder the old practice of flogging an innocent child in place of a misbehaving prince. We are surrounded by signs of the depravity of our ancestors’ way of life, but we are barely aware of them. Just as travel broadens the mind, a literal-minded tour of our cultural heritage can awaken us to how differently they did things in the past. In a century that began with 9/11, Iraq, and Darfur, the claim that we are living in an unusually peaceful time may strike you as somewhere between hallucinatory and obscene. I know from conversations and survey data that most people refuse to believe it.1 In succeeding chapters I will make the case with dates and data. But first I want to soften you up by reminding you of incriminating facts about the past that you have known all along. This is not just an exercise in persuasion. Scientists often probe their conclusions with a sanity check, a sampling of real-world phenomena to reassure themselves they haven’t overlooked some flaw in their methods and wandered into a preposterous conclusion. The vignettes in this chapter are a sanity check on the data to come.”